Comment on "A 'one pot' gel combustion strategy towards Ti3+ self-doped 'black' anatase TiO2−x solar photocatalyst," by S. G. Ullattil and P. Periyat, J. Mater. Chem. A, 2016, 4, 5854

In this work, it is shown that the high concentration of Ti 3+ in "black" anatase TiO 2− x , as claimed by Sanjay Gopal Ullattil et al. [Sanjay Gopal Ullattil et al. , J. Mater. Chem. A , 2016, 4 , 5854-5858], is inappropriate. Using the binding energy difference parameter ΔBE = BE(O 1s) − BE(Ti 2p 3/2 ) = 528.7 − 457.6 = 71.1 eV, the domination of the Ti 4+ state in the considered compound is verified. It is shown that the high concentration of Ti 3+ in "black" anatase TiO 2− x , as claimed by Sanjay Gopal Ullattil et al. [Sanjay Gopal Ullattil et al. , J. Mater. Chem. A , 2016, 4 , 5854-5858], is inappropriate. The Ti 4+ state is dominant in the considered compound.